Nodemailer API returns 404 and "Unexpected token 'T', 'The page c' is not valid JSON" when sending email from frontend [closed]

I am trying to send an email from my website using Nodemailer.
My frontend calls a backend API which sends the email.

However, when I trigger the email request from the frontend, I get the following errors in the browser console:

Failed to load resource: the server responded with a status of 404 () Error: SyntaxError: Unexpected token 'T', "The page c"... is not valid JSON at index-BhBzu5Md.js:333